Kernel idle interference??

["H. S. Teoh" <hsteoh@quickfur.yi.org>]

[Please Cc: replies to me, I'm not subscribed due to high volume.]

Recently, I noticed this very odd phenomenon with my sound card.  I'm
using an SB16 with the OSS drivers, and there is this persistent
background static hum, which is noticeably loud on my headphones. This hum
also has buzzes which coincides with hard drive accesses and mouse
movements. At first I thought it was due to bad hardware, or perhaps
broken/incompatible sound drivers; but one day, I got an idea and ran the
following program: 

	#include <unistd.h>
	void main() {
	  nice(19);
	  for(;;);
	}

I ran the program in the background, basically to eat up all idle CPU
cycles.  Amazingly, when this program is running, the static hum
disappears. When I kill it, the hum returns. 

Does anyone have any idea what might be causing this? I suspect it might
be something in the kernel idle loop that's causing this; but I've looked
over my kernel config several times and can't see any option that might
affect this. 

I'm using kernel 2.4.18 currently; the problem happens on both 2.4.16 and
2.4.18.

Any ideas/suggestions would be appreciated. Thanks.


T

-- 
There are three kinds of people in the world: those who can count, and those
who can't.


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